Rotary drill bits



Jan. 21, 1964 C. T. KAY

ROTARY DRILL BITS Filed Sept. 29, 1960 3 Sheets-Sheet 1 I0 F g. 3 l5 m,i 38 W W 3a A .9 la 2/ B 2 3 25 2 a 3 a; 3.; 32 V7 ig .73 32 Hg 4INVENTOR Cas/mir I Kay 20 ATTORNEYS Jan. 21, 1964 Filed Sept. 29, 1960ROTARY DRILL BITS 3 Sheets-Sheet 2 I/II ATTORNEYS Jan. .21, 1964 C. T.KAY

ROTARY DRILL BITS 3 Sheets-Sheet 3 Q /5 a 'lb .7/ 2a IN "WIN 32 .4 20 2/Flag 32 1a 27 m /7 24 MP [W l? 33 32 k7 ENTOR mv F g9 32 Cos/mir I KayATTORNEYS United States Patent 3,118,511 RQTARY DRILL BKTS Casimir T.Kay, 4135 W. 7th St, Dallas, Tex. Filed Sept. 29, 1960, Ser. No. 59,3012 Claims. (Cl. 175'-397) This invention relates to new and usefulimprovements in rotary drill bits.

The invention is specifically concerned with drill bits of the typehaving no revolving cutter cones or rollers, the invention beingespecially useful in relatively small and medium-sized drill bits.

An important object of the invention is to provide an improved rotarydrill bit in which the cutting faces, and particularly the hard tippingthereof, are concentrated in the outer portions of the formation facebeing drilled, with lesser areas of the cutting faces being positionedfor drilling or cutting of the inner portions of the formation face. Arotary drill bit cuts or drills a more or less circular hole, and theformation face against which the drill is operating is in theconfiguration of a circle. It is quite apparent that there is less ofthe formation to be drilled or cut in the inner or central portions ofthe formation face, and considerably greater areas in the outer portionsof the formation face being drilled. By concentrating the cutting ordrilling faces and especially the hard metal inserts carried thereby, inthe proper positions so as to drill predominantly upon the outerportions of the formation face, increased cutting action over thisprincipal area is made possible. In addition to which, in a given bit ofa given size and containing a given quantity of hard metal, such astungsten carbide, the hard metal may be concentrated so as to functionpredominantly upon the outer portions of the formation face, andaccordingly, hard metal inserts of greater thickness may be employed inthe bit without increased cost but with increased wearing life andfaster drilling.

Another object of the invention is to provide an improved rotary bithaving several blades, and in which the blades are not equidistantly orequi-angularly dis posed, with the result that the bit runs moresmoothly and the tendency of the bit to chatter as it revolves anddrills is largely eliminated.

A still further object of the invention is to provide an improved rotarybit having several cutting blades with cutting points thereon and inwhich the cutting points of the several blades are not rotationallyalined so that the cutting points do not track one another, but instead,travel in slightly different annular paths whereby faster and moreeffective drilling or cutting is achieved.

A still further object of the invention is to provide an improved rotarybit having several cutting blades in which the cutting faces of theblades are swept back both longitudinally as well as transversely orlaterally to cause the blades to drag over the formation, to help holdthe hard metal inserts in place in the cutting faces of the blades, andalso to provide an increased or greater wearing area on the hard rnetalinserts.

An additional object of the invention is to provide an improved rotarydrill bit having reduced blade area and cutting face area to cause thecutting faces to dig into the formation being drilled so that fasterdrilling may be obtained while simultaneously less downward thrust orweight need be applied to the bit.

A further object of the invention is to provide an improved rotary drillbit which is virtually equally effective in soft, medium, or hardformations so that there is no need to change the drill bit as strata ofvarying types of formation are encountered.

Yet another object of the invention is to provide an improved rotarydrill bit which eliminates all cutting faces from the central axis ofthe bit, it having been found that there is no need to drill the verycenter of the formation face since this small core is broken off duringbit rotation due to inherent wobbling or less than perfectly circularrotation of the drill bit.

A construction designed to carry out the invention will be hereinafterdescribed, together with other features of the invention.

The invention will be more readily understood from a reading of thefollowing specification and by reference to the accompanying drawings,wherein examples of the invention are shown, and wherein:

FIG. 1 is a side elevational view of a four-bladed rotary drill bitconstructed in accordance with this invention,

FIG. 2 is a bottom plan view of the drill bit of FIG. 1,

FIG. 3 is a diagrammatic view illustrating the cutting or drillingeffect observed from the use of the drill bit of FIG. 1,

FIG. 4 is a diagrammatic view illustrating the means by which increasedwearing surfaces are obtained,

FIG. 5 is a side elevational view, the top thereof being in section, ofa three-bladed drill bit constructed in accordance with this invention,

FIG. 6 is a bottom plan view of the drill bit of FIG. 5,

FIG. 7 is a view similar to FIG. 3 illustrating the cutting action ofthe drill bit of FIG. 5,

FIG. 8 is a vertical, sectional view taken on the line 8-8 of FIG. 2,

FIG. 9 is a vertical, sectional view taken on the line 99 of FIG. 6, and

FIG. 10 is a schematic view illustrating the negative rake and angularoffsetting of the cutting blades.

In the drawings, in FIG. 1 the numeral 16 designates a circular drillbit body having a plurality of spaced, depending drilling or cuttingblades and an upstanding, tapered, screwthreaded pin 11 for connectionto the lower end of the conventional drill collar or drill pipe. Asshown in FIGS. 2 and 8, the pin 11 is formed with an axial water course12, having a plurality of water passages 13 opening outwardly from itslower end into the spaces between the cutting blades, and having anaxial reduced water course 14 opening diametrically downwardly into thespace located centrally of the cutting blades.

The cutting blades are formed integrally with the drill body It? andinclude at their upper ends downwardly and outwardly inclined shoulders15 which merge into substantially vertical cutting or reaming edges 16formed on the outer edges of the drill blades and displaced radiallyoutwardly from the drill body It). The lateral, substantially vertical,reaming edges 16 of the cutting blades adjoin at their lower endsdownwardly and inwardly inclined cutting edges 17 terminating in obtusecutting points 18 on each of the cutting blades.

In the form of the invention illustrated in FIGS. 1 and 2, there arefour of the cutting blades, a diametrically opposed pair of the blades,19 and 2%, having inwardly :and upwardly inclined cutting edges 21extending approximately radially inwardly from the cutting points is ofsaid blades 19 and 2%). The combined widths of the cutting edges 17 ofthe blades 19 and 25 and of the cutting edges 21 thereof are such thatthe blades 19 and have an effective cutting width of approximatelyonequarter of the cutting diameter of the bit or of the hole beingdrilled by the bit. Thus, the cutter blades 19 and 2d and the cuttingedges thereof drill only the outermost portion of the bottom of thedrill hole, this being the portion shown as double. cross-hatched at 22in FIG. 3 and which represents an area of the magnitude of 75- 80% ofthe total area of the hole being drilled. As will be seen, this area isalso drilled by the other two cutting blades.

The third cutter blade 23 is disposed between and approximately at rightangles to the blades 19 and 2i) although it will be seen hereinafterthat this is not exactly true. The third cutter blade 23 is formed withan inwardly and upwardly extending cutting edge 24 projecting radiallyinwardly from the cutting point 18 of the blade 23 toward the axis ofthe drill bit to a point spaced about one-third of the distance betweenthe axis of the bit and the track of the inner extremities of thecutting edges 21 of the cutting blades 19 and 25). In addition,therefore, to drilling the area 22 shown in FIG. 3, the blade 23 alsocuts an additional inner area 25 indicated by cross-hatching in FIG. 3and representing 16-15% of the total cross-sectional area of the holebeing drilled.

The fourth cutter blade 26 is disposed more or less diametricallyopposite the blade 23 and has an inwardly and upwardly inclined cuttingedge 27 extending radially inwardly from the cutting point 18 of theblade 26 and to a point spaced approximately two-thirds of the distancebetween the inner margin of the cutting area 22 and the axis of thedrill bit. The blade 26, in addition to cutting the areas 22 and 25,thus in addition, cuts the innermost area 28, indicated in FIG. 3 byhatching, and representing 5-1 of the total bottom hole area beingdrilled. The very center portion of the drill hole bottom, indicated at29 in FIG. 3, is therefore not cut or drilled by any of the blades, ithaving been found that as the drill bit progresses downwardly through aformation, a small slender core will tend to form in the area 29, andthat this core will repeatedly be snapped off through the inherentwobbling or eccentric rotation of the drill bit so that there is noreason to expend cutting energy and cutting area thereon.

The drilling area percentages recited hereinabove are approximate onlyand are subject to variations, the important point being that the outerand predominantly larger area is subjected to the cutting action of allfour cutter blades, the next inner and next larger area being subjectedto the cutting action of two of the blades, and the innermost andsmallest area requiring the cutting action of only a single one of theblades. In this manner, the cutting areas of the several blades may belargely concentrated in the outer portions of the formation area andneedless and excessive cutting blade area in the center portions of thehole eliminated. This means not only that the drill bit will out fasterbecause the bit digs in due to the reduced blade area, but also, thatless weight is needed on the drill bit for obtaining the predetermineddrilling rate. This also means that the hard metal inserts, forinstance, tungsten carbide inserts, which will be described more fullyhereinafter, may be made of thicker configurations without increasingthe total weight of hard metal present in the bit and thereby increasingthe cost thereof. The presence of the thicker hard metal inserts meansthat the bit will drill faster, and will last longer, because of thegreater and the longer wear of the thicker inserts.

The hard metal cutting inserts for the reaming edges 16 may desirably beof an elongate rectangular shape and suitably secured, as by brazing orotherwise, in a rectangular groove 31 cut in the lateral edges of theseveral cutting blades. The hard metal inserts 32 forming the cuttingedges 17 desirably are of a trapezoidal shape and present a cutting edgedisposed at approximately 25 to the horizontal. The same hard metalinserts may be employed for forming the cutting edges 21 and the outerportions of the cutting edges 24 and 27, as indicated in FIGS. 1 and 2,and additional hard metal inserts 33 generally of parallelogram shapemay be employed for forming the additional and inner portions of thecutting edges 24 and 27, one of the inserts 33 being employed in theblade 23, as shown in FIGS. 1 and 2, and two of the inserts 33 beingemployed for the blade 26, as shown in FIG. 8. Such an arrangement is byno means essential, but is convenient for fabrication and for minimizingthe number of sizes and shapes of hard metal inserts which must beemployed. The inwardly and upwardly inclined portions of the severalcutting edges may also be inclined at an angle of approximately 25 tothe horizontal, the same as the outer cutting edges 17.

In the fabrication of bits of this type, the hard metal inserts arenormally fitted into complementary recesses formed in the edges of thecutting blades of the bit and therein secured by brazing or otherwise,following which the bit and the cutting edges thereof are ground to thedesired dimensions and shape. In carrying out the grinding operation, orat any other convenient point in the fabrication of the hits, thecutting points of the several cutting blades are desirably misalinedrotationally, or offset with respect to one another a distance of A ofan inch or so measuring radially of the bit. Thus, for instance, thecutting points of the blades 19 and 20 may be rotationally alined, whilethe cutting points of the blades 23 and 26 are offset of an inch or soinwardly or outwardly with respect to the track of the cutting points ofthe blades 19 and 20, or one offset inwardly and the other offsetoutwardly. This avoids the tendency of the cutting points to track oneanother and otherwise aids in the more effective and smooth operation ofthe bit.

Another important feature of the invention is that in forming theworking faces of the cutting blades, as by milling or otherwise, theblades are not evenly and equally spaced. Thus, assuming the blades 19and 20 to be spaced 180 from one another, either or both of the blades23 and 26 may be offset rotationally through an angle of 5-10 in eitherdirection from strict 90 positioning with respect to the blades 19 and20. A very effective angle of displacement has been found to be about 6.This shifting or misalining of the blades causes the drill bit to runmore smoothly and eliminates the chattering or vibration which seeminglyis a characteristic of drill bits having equally spaced cutting blades.Thus, instead of positioning the blade 23 at a 90 angle with respect tothe blade 20, it is desirably positioned at an angle of -100 withrespect to the blanc 19 and most desirably at an angle of 84-96".Similarly, the blade 26 may be oifset with respect to the blade 20 anangle other than or both the blades 23 and 26 may be so offset in eitherdirection.

As shown in FIGS. 1 and 2 the forward longitudinal faces of the cuttingblades have a negative rate or are sloped or inclined slightlyrearwardly from top to bottom from the direction of cutting or drillingrotation. In a lateral or radially outward direction, the cutting bladesalso have a negative rake and are sloped rearwardly and outwardly fromthe direction of rotation. In both instances, the angle of rake maydesirably be about 6, but may range from 5-10". This negative angle ofrake in both horizontal and vertical planes has several beneficialeffects, the first being that it causes the cutting edges of the bit tomore or less drag over the formation being cut or drilled to provide asmoother and more effective cutting action with a minimum of vibrationand chattering of the drill bit. Contrary to erroneous suppositions,drill bits of this type do not cut an earth formation in the manner inwhich a knife cuts an object, but instead, they wear, grind and scrapeaway the formation through an attrition process, and accordingly, theenhanced dragging action effected through the negative raking of thecutting blades has been found quite conducive to improved drillingoperation.

As a second beneficial result, the negative raking of the blades reducesthe tendency for the hard metal inserts to be ripped or torn from thedrilling blades as the drill revolves. It is characteristic of drillingbits having hard metal inserts that the inserts are sometimes dislodgedfrom the bit and lose their efiicacy as drilling or cutting surfacesbesides adding to the possible accumulation of debris in the Well bore.The negative raking of the blades results in less stress being placedupon the bond between the hard metal inserts and the drill body, andaccordingly, there is less tendency for the inserts to be forced fromtheir bonded or brazed positions.

The third benefit of raking the cutting blades is illustrated on anenlarged scale in FIG. 4 of the drawings in which one of the hard metalinserts is shown in crosssection. The inserts wear, of course, at rightangles to the axis of the bit, and if the inserts are verticallypositioned so as to be parallel to the bit axis, the inserts will wearalong the transverse line A shown at the top of FIG. 4. If, however, theinserts are inclined with respect to the bit axis, the inserts willstill wear in a plane perpendicular to said axis which will be alongline B shown in the middle portion of FIG. 4. Obviously, line B islonger than line A, and the inclined inserts will necessarily present agreater wearing area, because of the greater cross section at thewearing plane, to the bottom of the drill hole. It is noted that thiswill also be true of the hard metal inserts disposed along the lateralcutting or reaming edges 16.

A modified form of the invention is shown in FIGS. 5, 6 and 9, this formof the drill bit having three cutting lades rather than four. In allother respects, the modified form of the bit is essentially the same asthat first described, and both bits include the same features andfunction in very much the same manner. In essence, the cutting blade 19is deleted from the bit body and the blades 23 and 26 are shifted sothat the three blades 20, 23 and 26 are disposed approximately 120apart. Of course, as pointed out in connection with the first form ofthe invention, one or two of the blades should be offset from 5l0 froman exact 120 positioning in order to provide a smoother running bit andto eliminate the tendency of the bit to chatter. The offsetting of thecutting points, the negative rake of the cutting blades both verticallyand laterally, and the concentration of the cutting surfaces in theouter portion of the area being drilled are all features common to bothforms of the bit, and the several attendant advantages will not berepeated. As shown in FIG. 7 the outermost portion 34 of the bottom ofthe hole and which is shown in FIG. 7 as hatched and cross-hatched,represents approximately 75-80% of the total area of the hole beingdrilled, this area being drilled or cut by all three of the cutingblades of this second form of the invention. The next innermost area 35,shown as cross-hatched in FIG. 7 and representing 10- of the totalcross-sectional area of the hole being drilled, is engaged by the innerportions of both the blades 23 and 26, while the innermost area 36,shown as hatched in FIG. 7 and representing 5-l0% of the crosssectionalarea, is drilled only by the innermost portion of the cutting blade 26.The primary difference in action, thus, is that the second form of theinvention includes only a single cutting blade for functioning solely inthe outermost area 34, and that the latter area is subjected to thedrilling action of three blades rather than four. As to the areas 35 and36, there is no difference of function, the inner core 3 7 not beingsubjected to drilling action but being readily snapped off at frequentintervals as the drill bit inherently wobbles or rotates eccentricallyin its operation.

The longitudinal negative rake of the cutting blades in both forms ofthe invention is clearly shown in FIGS. 1

and 5, but the negative rake in a lateral or radial direction is notquite so apparent in the bottom plan views.

This arrangement is shown schematically in FIG. 10, the hetero-angulardisposition of the blades being illustrated as the 5 offsetting orshifting of the left-most blade 38. The upper blade 39 and right-mostblade 40 are spaced apart, but the blade 38 has been shifted 5 towardthe blade 39 so as to lie l'l5 therefrom, and from blade 40. Of course,two of the cutting blades may be shifted so that none of the blades lieexactly 120 from the remaining blades. In the case of the four bladedrill bit, the shifting would be from a 90 angular relationship.

The negative lateral rake of the cutting edges of the blades is alsomore readily apparent from an examination of FIG. 10, it being notedthat each of the blades slants rearwardly and outwardly from thedirection of rotation of the bit, the particular rake shown being 5. Inthe case of the blade 38, it is noted that this negative rake of 5 is inaddition to the 5 by which the entire cutting blade is shifted withrespect to blades 39 and 40'.

In both forms of the invention, the drilling action is concentrated inthe outer area of the formation face being drilled, permitting theutilization of more or greater masses of hard metal inserts in this areawith the resultant faster drilling and longer operating life. The bitsalso drill faster because the blade area is reduced allowing the bit todig in more effectively while reducing the weight which need be appliedto the bit along with the resultant wear thereon.

Both drill bits function quite effectively in soft, medium or hardformations so that there is no need to change bits as the formation inthe well bo-re may change from time to time although one of the bits maybe preferable to the other when certain types of formation areencountered consistently. In both instances one or two of the cuttingblades are shifted 5l0 from exact equi-distant or equiangular spacingfrom the remaining blades, and all of the cutting blades are formed witha negative angle or rake both vertically and horizontally. In bothinstances, the cutting points are olfset rotationally with respect toone another so as to eliminate tracking of the cutting points, and inboth instances, the carrying out of drilling at the exact center of thedrill bore is eliminated as being unessential, permitting additionalconcentration of cutting surfaces.

The foregoing description of the invention is explanatory thereof andvarious changes in the size, shape and materials, as well as in thedetails of the illustrated construction may be made, within the scope ofthe appended claims, without departing from the spirit of the invention.

What I claim and desire to secure by Letters Patent is:

1. A rotary drill bit including, a drill body, drilling blades dependingfrom the body, cutting edges on the lower ends of the drilling bladesextending from the periphery of the bit approximately radially inwardlythereof, the cutting edge of one of said blades extending fartherinwardly than the cutting edge of another of said blades, the peripheraledges of the cutting edges being spaced apart circumferentially of thedrill body unequally, the cutting edges being V-shaped in configurationalong vertical planes extending radially of the drill body so as to havedepending vertices, and the vertices being spaced radially outwardlyfrom the center of the drill body different distances and misalinedrotationally.

2. A rotary drill bit including, a drill body, drill-ing bladesdepending from the body, cutting edges on the lower ends of the drillingblades extending from the periphery of the bit approximately radiallyinwardly thereof, the cutting edge of one of said blades extendingfarther inwardly than the cutting edge of another of said blades, theperipheral edges of the cutting edges being spaced apartcircumferentially of the drill body unequally, the cutting edges beingV-shaped in configura- 7 lion along vertical planes extending radiallyof the drill body so as to have depending vertices, and the verticesbeing spaced radially outwardly from the center of the drill bodydifferent distances and misalined rotationally by a. distance of theorder of magnitude of one-sixteenth of an inch.

References Cited in the file of this patent UNITED STATES PATENTS1,218,671 Lane Mar. 13, 1917 10 8 Zub1in Mar. 23, 1937 Hughes Jan. 9,1940 Phipps May 9, 1950 Rassieur Aug. 25, 1953 Stokes June 4, 1957SteflFes Jan. 24, 1961 FOREIGN PATENTS Great Britain Dec. 5, 1940 GreatBritain Feb. 11, 1941

1. A ROTARY DRILL BIT INCLUDING, A DRILL BODY, DRILLING BLADES DEPENDINGFROM THE BODY, CUTTING EDGES ON THE LOWER ENDS OF THE DRILLING BLADESEXTENDING FROM THE PERIPHERY OF THE BIT APPROXIMATELY RADIALLY INWARDLYTHEREOF, THE CUTTING EDGE OF ONE OF SAID BLADES EXTENDING FARTHERINWARDLY THAN THE CUTTING EDGE OF ANOTHER OF SAID BLADES, THE PERIPHERALEDGES OF THE CUTTING EDGES BEING SPACED APART CIRCUMFERENTIALLY OF THEDRILL BODY UNEQUALLY, THE CUTTING EDGES BEING V-SHAPED IN CONFIGURATIONALONG VERTICAL PLANES EXTENDING RADIALLY OF THE DRILL BODY SO AS TO HAVEDEPENDING VERTICES, AND THE VERTICES BEING SPACED RADIALLY OUTWARDLYFROM THE CENTER OF THE DRILL BODY DIFFERENT DISTANCES AND MISALINEDROTATIONALLY.